1. Field of the Invention
The present invention relates generally to a passenger conveyor such as an escalator, and more particularly to an upper rail for a passenger conveyor capable of reducing noises and vibrations generated due to the impact of the rear wheel roller of a step during its operation.
2. Description of the Related Art
A passenger conveyor typically includes a series of passenger platforms which are driven in an endless path between horizontally spaced landings. The most common types of passenger conveyors are escalators and horizontal walkways. In case of the escalator, the platforms are steps which are driven between an upper landings and a lower landing to facilitate the conveyance of passengers, cargo, and the like. The passenger conveyor also includes hand rails which are movable along and supported by opposite sides of a main frame of the conveyor.
The passenger platforms are normally connected in a circle by a pair of drive chains which extend along opposite sides of the passenger conveyor and which engage a drive sprocket assembly mounted on at least one end of the conveyor to effect continuous movement of the steps between the upper and lower landings. The steps extend laterally across the conveyor between the opposite sides of the main frame to define a step band that is a spatial envelope between the upper and lower landings and between the opposite handrails through which the steps travel. The steps, which convey passengers toward an off-load landing, travel above the sprocket assembly to define an upper step band, while the inverted steps which return to the on-load landing, travel below the sprocket assembly to define a lower band.
Such a conventional passenger conveyor will be explained in detail with reference to FIGS. 1 to 9. Referring to FIGS. 1 and 2, the conventional passenger conveyor comprises a pair of horizontally spaced circulating hand rails 1, a plurality of steps 2 which passengers get on and off, and a transmission system 3 for driving the handrails 1 and the steps 2. The transmission system 3 generally includes a motor 4 for driving the steps 2, a speed reducer 5 for transferring the driving force between the motor and a drive sprocket 7, and drive chains 6 operatively engaged with the drive sprocket 7. The driving force is produced from the motor 4 and transferred to the speed reducer 5 engaged directly to the motor. The driving force is transferred to the drive chains 6 by the drive sprocket 7 engaged with the speed reducer 5. The driving terminal gear 8 coupled coaxially to the drive sprocket 7 drives the drive chains 6 engaged with the steps 9. The steps travel upwardly and downward along the driving and driven terminal gears 8 and 11. Finally, the steps travel to convey passengers from a lower or upper floor to an upper or lower floor.
FIG. 3 illustrates a conventional upper rail 16, and FIGS. 4 and 5 illustrate an enlarged state of the conventional upper rail. As shown in FIG. 4, the steps rotate along the terminal gear 8 on the upper rail 16 of the passenger conveyor. The rear wheel roller 14' of the step rolls along the terminal rail 13, and the front wheel roller 14 of the step moves along the upper rail 16.
With the above structure, when the step chains 10 engaged with the front wheel roller 14 of the step couple to the terminal gear 8, the contact of the metals will produce shock sounds, there has been proposed a method in that the step chains can be coupled to the terminal gear with no strong impact by adjusting the position of the upper rail, which will be now explained with reference to the accompanying drawings.
FIG. 3 illustrates the structure of the conventional upper rails consisting of a arched section 18 and a straight section 19. The arched section 18 has a curvature of 200 millimeters and a length of 40 millimeters, and the straight section has a thickness of 16 millimeters, both of which are made of a mild steel. Width of the structure of the upper rails is of a somewhat wider than it of the front wheel roller 14. The upper rails 16 are disposed on each side of the conveyor and are secured by a bracket 30 of a frame 25 of the upper rail. The height of the upper rail 16 can be adjusted by interposing a thin metal piece such as a liner between the bracket 30 and the upper rail 16, or by bolting, welding or riveting.
As shown in FIG. 4, the height of the upper surface of the upper rail 16 positions below the front wheel roller 14 by a radius of the front wheel roller 14 of the step, and back and forth positions thereof are assembled in such a manner that the starting section of the arched section 18 coincides with the perpendicular center line of the terminal gear 8. Sometimes, for the purpose of reducing noises and vibrations the upper rail 16 is assembled at the position, about 3-4 millimeters, higher than the bracket 30.
When the conveyor moves, the step 9 travels in a clockwise or counter-clockwise direction by the drive terminal gear 8 and the driven terminal gear 11. As shown in FIGS. 1 and 2, the step chains 10 are moved by the drive terminal gear during moving. The front wheel roller 14 coupled to the step chains rolls along the upper rail 16, and the rear wheel roller 14' rolls along the terminal rail 13. Referring to FIGS. 4 and 5, the straight section and the arched section 10 of the upper rail positioned near the terminal gear performs the role of guiding to smoothly engage at an abutting portion 20 when the step chains are coupled to the terminal gear 8.
The front wheel roller of the step moves upward or downward to some extent, when it leaves from or lands on the arched section. This movement causes the front wheel roller of the step to leave or lands smoothly.
Because the terminal gear made of a mild steel rotates the step chains made of a steel, however, the vibrations and noises can be inevitably produced by the impact at the abutting portion which the step chains are coupled to the terminal gear as shown in FIGS. 4 and 5.
In order to prevent the impact phenomenon from being produced, the position to be coupled with the front wheel roller 14 and the step chains 10 is compensated by lifting the height of the upper rail 16 so that the step chains 10 may be coupled to the terminal gear 8 without occurring the impact at the abutting portion. If the position of the upper rail is adjusted higher to relief the impact, in case that the conveyor rotates in a clockwise direction, i.e., the steps ascend, no impact occurs at the abutting portion 20, thereby not producing the noise, as shown in FIGS. 6 and 7. In case the conveyor rotates in a counter-clockwise direction, thus the steps descend, the front wheel roller 14 of the step applies the strong impact to the arched section 18 of the upper rail, thereby producing the loud impacting sound, as shown in FIGS. 8 and 9.
When the conventional passenger conveyor moves which the upper rail is engaged in a normal condition, the noises and vibrations are produced from the abutting portion 20 of the terminal gear disposed in the upper of the conveyor. The noises and vibrations caused by the impact has been the chronic an inherent problem of the conventional conveyor in spite of continuous efforts to solve it.
In order to examine all possible factors of the above noises and vibrations, the noise measuring test was carried out by using so-called Taguji method. The testing result has revealed that the source of the periodical noises at the upper arched section of the conveyor is the impact of the terminal gear 8 and the step chains 10 at the abutting portion 20.
In order to eliminate or reduce the impacting sound as described above, the conventional passenger conveyor was incorporated with a method of lifting the height of the upper rail to prevent the step chains from impacting against the terminal gear at the abutting portion.
In the above method, however, in case the conveyor rotates in a clockwise direction thus the steps ascend, there is no happened any impact at the abutting portion, thereby no producing the noises. Meanwhile, in case the conveyor rotates in an counter-clockwise direction, thus the steps descend, the front wheel roller of the step applies strong impact to the arched section of the upper rail, thereby producing a loud impacting sound, as shown in FIGS. 8 and 9. At that time, the upper rail moves vertically, so the loud impacting sounds and vibrations are produced. Such a phenomenon is produced that because the arched section of the upper rail has a relatively shorten curved line, if the height of the upper rail is higher than the normal conditions, the terminal portion of the arched section 18 deviates from the trace of the front wheel roller of the step, depending upon the curvature of the terminal gear, as shown in FIGS. 8 and 9.
Summarizing the problems as mentioned above, in case of assembling the upper rail according to the normal fixing standards, the impacting sounds will be produced from the abutting portion 20, at every time the steps rotate in a clockwise or counter-clockwise direction. In case the upper rail is assembled at a higher position than the normal fixing standards, the front wheel roller 14 of the step strikes against the arched section 18 to produce a loud impacting sound.